1. Field of the Invention
The present invention relates to a carrying device for carrying semiconductor wafers from a wafer carrier to a sampling inspection device or loading the inspected semiconductor wafers into the wafer carrier.
2. Description of the Prior Art
Recently, in order to reduce labor expenses and increase throughput, surface inspection of processed wafers has been automated, and therefore many carrying devices for carrying wafers from a wafer carrier to a sampling inspection device or loading the inspected wafers into the wafer carrier have been developed. For example, as shown in FIG. 8, a prior art wafer carrying device consists of an elevatable carrier station 3a for receiving wafer carrier 30, a carrying arm 2a for a carrying semiconductor wafer 5, a horizontally rotatable wafer stage 8 for receiving the wafer 5 and a guide 9 mounted at the periphery of the wafer stage 8 for determining the position of the wafer 5. When the wafers 5 is to be placed on the wafer stage 8, the positioning of each wafer is then determined by the guide 9, and the wafer 5 is placed on a plurality of protrusions 81 which are provided on the periphery of the wafer stage 8.
However, if the wafer 5 loaded into the carrier 30 or the wafer 5 placed on the wafer stage 8 from other carrying devices (not shown) can not be positioned precisely, they will drop from the wafer stage 8.
In particular, the influence of inertia exists when a semiconductor wafer is not precisely positioned on the rotating wafer stage. As diameter of the semiconductor wafer is increased, the influence of inertia is larger. To improve this, in Japanese Patent Laid Open 7-273171, a "handling device for discal objects" is proposed. According to this device, by providing a centering guide shoe for positioning the semiconductor wafer and an sucking stand for sucking a bottom surface of a semiconductor wafer to a rotating stage, the rotating wafer is not moved and firmly supported.
However, according to the above-mentioned "handling device for discal objects", although the rotating semiconductor wafer can be firmly supported on the stage, the structure of the stage inevitably becomes complicated, and thus leading to such problems as the device is large and the fabrication cost is high.
Moreover, when carrying semiconductor wafers of different diameters, a change of different stages or the equipping of a plurality of carrying devices for carrying semiconductor wafers of different diameters is required in order to match with semiconductor wafers of different diameters.